The following abbreviations are utilized herein:
AC alternating current
DC direct current
ITO indium tin oxide
LCD liquid crystal display
LED light emitting diode
RC resistor-capacitor
Electronic devices generally include a display for presenting information to the user. FIG. 1 shows a top view of an exemplary display module 150 for an electronic device. The display module 150 includes a display panel 152 that is controlled by a display driver/controller 154. A flexible printed cable 156 and a connector 158 enable connection of the display driver 154 to other components of the electronic device, such as a power source (e.g., battery) and/or another controller (e.g., one or more processors). As a non-limiting example, the display driver 154 may comprise an integrated circuit suitable for controlling the display of information (e.g., data, images) on the display panel 152. As a non-limiting example, the display panel 152 may comprise a LCD. As a non-limiting example, the electronic device may comprise a mobile device, such as a portable computer or a mobile phone, for example.
A LCD is an electronically-modulated optical device shaped into a thin, flat panel and comprised of a number of pixels filled with liquid crystals and arrayed in front of a light source (backlight) or reflector. LCDs are often employed in battery-powered electronic devices because they use comparatively small amounts of power. As a non-limiting example, the light source may comprise one or more LEDs.
FIG. 2 shows a side view of the exemplary display module 150 of FIG. 1. The display panel 152 is comprised of a number of components. An upper glass 160 may be disposed above a layer of liquid crystal material 162 comprised of color filters. The layer of liquid crystal material 162 may be disposed on a bottom glass 164. The display driver 154 may be situated on (e.g., connected to or connected via) the bottom glass 164, as may one end of the flexible printed cable 156. Underneath the bottom glass 164 may be a light source, such as a LED 166. A light guide 168 may enable the transfer of the light 170 from the LED 166 to illuminate the display panel 152. In other display modules, a prism sheet or other component may be utilized to improve the illumination uniformity of the display panel 152.
FIG. 3 shows a side view of the exemplary display driver 154 of FIG. 1. The display driver/controller 154 includes a plurality of connectors which may comprise, as a non-limiting example, a plurality of bumps 172. The connectors (bumps 172) allow the display driver 154 to communicate with and/or control other components of the mobile device, including the display panel 152. Light 174, such as light from the LED 166, is incident upon the bottom (underside) of the display driver 154. FIG. 4 shows a bottom view of the exemplary display driver 154 of FIG. 3.
The light 174 (e.g., energy from the light) can interfere with operations of the display driver 154, for example, by changing or affecting register values. As such, it is desirable to protect at least the bottom of the display driver 154 from incident light. One technique for providing this protection is to use an additional metal layer on the surface of the display driver 154.
FIG. 5 shows a side view of an exemplary display driver 176 that includes a protective layer 178. The connectors, such as bumps 180, may protrude beyond the protective layer 178 to provide connection(s) with one or more other components of the display module and/or mobile device. As a non-limiting example, the protective layer 178 may be comprised of a metal, and serves to protect the bottom of the display driver 176 from incident light 182. FIG. 6 shows a bottom view of the exemplary display driver 176 of FIG. 5. The protective layer 178 preferably does not otherwise interfere with operations of the display driver 176.
Generally, one cannot integrate all of the capacitors needed on the display driver 154. Therefore, external capacitors, disposed on the flexible printed cable, are often utilized. FIG. 7 depicts the use of external capacitors 186 on the flexible printed cable 156 of FIG. 1. The external capacitors 186 may be coupled to the display driver 154 (mounted on the bottom glass 164) via ITO traces 188. On the other side, the external capacitors 186 may be coupled to the other components via the foil trace 190. It should be noted that the trace is a conductive material (e.g., copper).
A capacitor is an electrical component comprised of two conductors separated by a nonconductive region. The nonconductive region may be referred to as a dielectric medium or dielectric layer, though the region may be comprised of air, a vacuum, a dielectric or a semiconductor depletion region chemically identical to the conductors, as non-limiting examples. When a voltage potential difference occurs between the two conductors, an electric field occurs in the insulator (the nonconductive region). This electric field can be used to store energy, to resonate with a signal, or to link electrical forces, as non-limiting examples. While capacitors are generally manufactured as electronic components for use in electrical circuits, any two conductors linked by an electric field display this property. Generally, the effect is greatest between wide, flat, parallel, narrowly-separated conductors. Capacitors pass AC signals but block DC signals.
An ideal capacitor is often characterized by a constant value, capacitance, given as a ratio of the amount of charge in each conductor to the potential difference between them. The unit of capacitance is thus coulombs per volt, or farads. Higher capacitance indicates that more charge may be stored at a given energy level, or voltage. In actual capacitors, the insulator allows a small amount of current through, called leakage current, the conductors add an additional series resistance, and the insulator has an electric field strength limit resulting in a breakdown voltage.
Capacitive coupling refers to the use of a capacitor to transfer energy. That is, capacitive coupling enables the transfer of energy (e.g., within an electrical system or network) by means of the capacitance between the two conductors. Capacitive coupling favors transfer of the higher frequency components of a signal, whereas inductive coupling (the transfer of energy using inductance) favors lower frequency components, and conductive coupling (the transfer of energy using conductors) favors neither higher nor lower frequency components. In this context, capacitive coupling may also be considered contactless signal transmission via the electrostatic effect induced between the two conductors (the capacitance across the two conductors).
In FIGS. 1 and 2, the exemplary display module 150 may be coupled to other components via the flexible printed cable 156 and the connector 158. This electrical coupling may be achieved by a direct connection (i.e., a contact connection) using the connector 158. There are other, contactless techniques for coupling a display module.
FIG. 8 shows a perspective view of an exemplary contactless display module 210. The display module 210 is comprised of two components: a receiving panel 212 and a transmitting board 214. The receiving panel 212 includes a LCD display 216, receiver circuitry 218 and a number of receiver electrodes 220. The transmitting board 214 includes a number of transmitter electrodes 222 and transmitter circuitry 224. The transmitter circuitry 224 may receive display data signals and a power signal from other components (not shown). The receiver electrodes 220 and the transmitter electrodes 222 are capacitively coupled to enable the transmission of signals (e.g., the display data signals) from the transmitting board 214 to the receiving panel 212. Note that the receiver electrodes 220 and the transmitter electrodes 224 are not in direct contact with one another (i.e., they do not physically touch). A capacitive connection (between the two sets of electrodes) is used instead of a conductive connection (e.g., a direct connection using contacts or connectors).
FIG. 9 shows a side view of the exemplary contactless display module 210 of FIG. 8. The receiving panel 212 may include two layers of glass substrate 226, 228 between which the receiver electrodes 220 are sandwiched. The receiving panel 212 may be disposed above the transmitting board 214 such that the receiver electrodes 220 and the transmitter electrodes 222 are separated by the nonconductive material of the glass substrate 228.